scholarly journals Analysis of non-diffuse characteristics of the seismic noise field in southern California based on correlations of neighbouring frequencies

2017 ◽  
Vol 212 (2) ◽  
pp. 798-806 ◽  
Author(s):  
Xin Liu ◽  
Yehuda Ben-Zion
Keyword(s):  
Seismic Noise ◽  
Southern California ◽  
Noise Field

scholarly journals Imaging New Zealand's Crustal Structure Using Ambient Seismic Noise Recordings from Permanent and Temporary Instruments

2021 ◽  
Author(s):  
◽  
Yannik Behr
Keyword(s):  
Seismic Noise ◽  
Cross Correlation ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Ambient Seismic Noise ◽  
Uppermost Mantle ◽  
Noise Sources ◽  
Noise Field ◽  
Rayleigh And Love Waves ◽  
Noise Cross Correlation

<p>We use ambient seismic noise to image the crust and uppermost mantle, and to determine the spatiotemporal characteristics of the noise field itself, and examine the way in which those characteristics may influence imaging results. Surface wave information extracted from ambient seismic noise using cross-correlation methods significantly enhances our knowledge of the crustal and uppermost mantle shear-velocity structure of New Zealand. We assemble a large dataset of three-component broadband continuous seismic data from temporary and permanent seismic stations, increasing the achievable resolution of surface wave velocity maps in comparison to a previous study. Three-component data enables us to examine both Rayleigh and Love waves using noise cross-correlation functions. Employing a Monte Carlo inversion method, we invert Rayleigh and Love wave phase and group velocity dispersion curves separately for spatially averaged isotropic shear velocity models beneath the Northland Peninsula. The results yield first-order radial anisotropy estimates of 2% in the upper crust and up to 15% in the lower crust, and estimates of Moho depth and uppermost mantle velocity compatible with previous studies. We also construct a high-resolution, pseudo-3D image of the shear-velocity distribution in the crust and uppermost mantle beneath the central North Island using Rayleigh and Love waves. We document, for the first time, the lateral extent of low shear-velocity zones in the upper and mid-crust beneath the highly active Taupo Volcanic Zone, which have been reported previously based on spatially confined 1D shear-velocity profiles. Attributing these low shear-velocities to the presence of partial melt, we use an empirical relation to estimate an average percentage of partial melt of < 4:2% in the upper and middle crust. Analysis of the ambient seismic noise field in the North Island using plane wave beamforming and slant stacking indicates that higher mode Rayleigh waves can be detected, in addition to the fundamental mode. The azimuthal distributions of seismic noise sources inferred from beamforming are compatible with high near-coastal ocean wave heights in the period band of the secondary microseism (~7 s). Averaged over 130 days, the distribution of seismic noise sources is azimuthally homogeneous, indicating that the seismic noise field is well-suited to noise cross-correlation studies. This is underpinned by the good agreement of our results with those from previous studies. The effective homogeneity of the seismic noise field and the large dataset of noise cross-correlation functions we here compiled, provide the cornerstone for future studies of ambient seismic noise and crustal shear velocity structure in New Zealand.</p>

Investigation of the spatial and temporal characteristics of the New Zealand seismic noise field.

2009 ◽  
Vol 125 (4) ◽  
pp. 2536-2536
Author(s):  
Laura A. Brooks ◽  
John Townend ◽  
Yannik Behr ◽  
Peter Gerstoft ◽  
Stephen Bannister
Keyword(s):  
New Zealand ◽  
Seismic Noise ◽  
Temporal Characteristics ◽  
Noise Field ◽  
Spatial And Temporal Characteristics

Modulation of seismic noise near the San Jacinto fault in Southern California: Origin and observations of the cyclical time dependence and associated crustal properties

2020 ◽  
Author(s):  
Vladislav G Martynov ◽  
Luciana Astiz ◽  
Debi Kilb ◽  
Frank L Vernon
Keyword(s):  
Seismic Noise ◽  
Southern California ◽  
Low Frequency ◽  
Ocean Waves ◽  
Seismic Attenuation ◽  
Phase Lag ◽  
Low Frequencies ◽  
San Jacinto Fault ◽  
San Jacinto Fault Zone ◽  
Seismic Quality Factor

Summary We examine the cyclic amplitude variation of seismic noise recorded by continuous three-component broadband seismic data with durations spanning 91 to 713 days (2008–2011) from three different networks: Anza seismic network, IDA network and the Transportable seismic array. These stations surround the San Jacinto Fault Zone (SJFZ) in southern California. We find the seismic noise amplitudes exhibit a cyclical variation between 0.3 and 7.2 Hz. The high frequency (≥ 0.9 Hz) noise variations can be linked to human activity and are not a concern. Our primary interest is signals in the low frequencies (0.3–0.9 Hz), where the seismic noise is modulated by semi-diurnal tidal mode M2. These long-period (low frequency) variations of seismic noise can be attributed to a temporal change of the ocean waves breaking at the shoreline, driven by ocean tidal loading. We focus on the M2 variation of seismic noise at f = 0.6 Hz, travelling distances of ∼92 km through the crust from offshore California to the inland Anza, California, region. Relative to the shoreline station, data from the inland stations show a phase lag of ∼ –12°, which we attribute to the cyclic change in M2 that can alter crustal seismic attenuation. We also find that for mode M2 at 0.6 Hz, the amplitude variations of the seismic quality factor (Q) depend on azimuth and varies from 0.22 per cent (southeast to northwest) to 1.28 per cent (northeast to southwest) with Q = 25 for Rayleigh waves. We propose the direction dependence of the Q variation at 0.6 Hz reflects the preferred orientation of sub-faults parallel to the main faulting defined by the primarily N45° W strike of the SJFZ.

scholarly journals Tomographic Imaging of the Agung-Batur Volcano Complex, Bali, Indonesia, From the Ambient Seismic Noise Field

2020 ◽  
Vol 8 ◽  
Author(s):  
Zulfakriza Zulfakriza ◽  
Andri D. Nugraha ◽  
Sri Widiyantoro ◽  
Phil R. Cummins ◽  
David P. Sahara ◽  
...  
Keyword(s):  
Seismic Noise ◽  
Tomographic Imaging ◽  
Ambient Seismic Noise ◽  
Noise Field ◽  
Batur Volcano

scholarly journals Microseisms in geothermal exploration—studies in Grass Valley, Nevada

Geophysics ◽  
1979 ◽  
Vol 44 (6) ◽  
pp. 1097-1115 ◽  
Author(s):  
Alfred L. Liaw ◽  
T. V. McEvilly
Keyword(s):  
Seismic Noise ◽  
Velocity Structure ◽  
Hot Spring ◽  
Body Wave ◽  
Sedimentary Cover ◽  
Source Region ◽  
Body Waves ◽  
Rock Properties ◽  
Noise Field ◽  
Short Period

Frequency(f)‐wavenumber(k) spectra of seismic noise in the bands 1 ⩽ f ⩽ 10 Hz in frequency and |k| ⩽ 35.7 cycles/km in wavenumber, measured at several places in Grass Valley, Nevada, exhibit numerous features which can be correlated with variations in surface geology and sources associated with hot spring activity. Exploration techniques for geothermal reservoirs, based upon the spatial distribution of the amplitude and frequency characteristics of short‐period seismic noise, are applied and evaluated in a field program at this potential geothermal area. A detailed investigation of the spatial and temporal characteristics of the noise field was made to guide subsequent data acquisition and processing. Contour maps of normalized noise level derived from judiciously sampled data are dominated by the hot spring noise source and the generally high noise levels outlining the regions of thick alluvium. Major faults are evident when they produce a shallow lateral contrast in rock properties. Conventional seismic noise mapping techniques cannot differentiate noise anomalies due to buried seismic sources from those due to shallow geologic effects. The noise radiating from a deep reservoir ought to be evident as body waves of high‐phase velocity with time‐invariant source azimuth. A small two‐dimensional (2-D) array was placed at 16 locations in the region to map propagation parameters. The f‐k spectra reveal shallow local sources, but no evidence for a significant body wave component in the noise field was found. With proper data sampling, array processing provides a powerful method for mapping the horizontal component of the vector wavenumber of the noise field. This information, along with the accurate velocity structure, will allow ray tracing to locate a source region of radiating microseisms. In Grass Valley, and probably in most areas of sedimentary cover, the 2–10 Hz microseismic field is predominantly fundamental‐mode Rayleigh waves controlled by the very shallow structure.

scholarly journals Fundamental and higher-mode Rayleigh wave characteristics of ambient seismic noise in New Zealand

2021 ◽  
Author(s):  
L Brooks ◽  
John Townend ◽  
P Gerstoft ◽  
S Bannister ◽  
Lionel Carter
Keyword(s):  
Seismic Noise ◽  
Ocean Wave ◽  
Wave Frequency ◽  
Ambient Seismic Noise ◽  
Continental Margins ◽  
Frequency Range ◽  
Dispersive Waves ◽  
Noise Field ◽  
Source Regions ◽  
American Geophysical

In order to use ambient seismic noise for mapping Earth's structure, it is important to understand the spatiotemporal characteristics of the noise field. This study uses data collected during four austral winter months of 2002 to investigate New Zealand's ambient seismic noise field in the double-ocean-wave-frequency range (0.1-0.3 Hz). It is shown via beamforming analysis that there are two distinct dispersive waves in the data. These waves can be separated. Their estimated phase velocities (2.5-2 and 4-3 km/s in the frequency range 0.14-0.25 Hz) match well with fundamental and higher-mode Rayleigh dispersion curves. Studies of double-wave-frequency microseisms elsewhere generally show the Rayleigh noise fields to be dominated by fundamental mode waves. The reason why higher-mode signals are observed here may reflect a combination of long ocean wave periods, large waveheights, the direct deep water approach to narrow continental margins, and the proximity of the seismograph array to the source regions. Copyright 2009 by the American Geophysical Union.

Sign in / Sign up

Export Citation Format

Share Document